User Manual Manual

871TM Extended Range User Manual
2
MOUNTING
CONSIDERATIONS Mounting considerations for shielded 871TM Extended Range units are essentially identical to those
of any inductive proximity sensor. The unshielded models, however, require special mounting
considerations as a result of their response to nonferrous metals. Due to the unusually long sensing
ranges of the 871TM Extended Range, the s ensing field extends farther back on the barrel and has
a wider diameter than typical devices. This increased field requires any metal mounting hardware be
placed as far back on the sensor barrel as possible to avoid interference and false triggering. When
selecting mounting hardware the recommended bracket materials are stainless steel or plastic—
especially in the c ase of the 30mm units. For assistance determining the best mounting hardware for
your application, consult your Rockwell Automation representative.
MAGNETIC FIELDS All inductive proximity switches are affected by external alternating magnetic fields whose
frequencies lie close to the sensor’s operating frequency. Unlike standard inductive proximity
sensors whose operating frequencies lie in the region of a few 100kHz, the 871TM Extended Range
family operates in the area of a few kHz. In particular, 50Hz magnetic fields with high harmonic
content, such as stray fields from mains transformers as well as near by stepping motors, can lead to
problems with the 871TM Extended Range. However, the potential for these sensors to be
influenced by switching power supplies (induction heaters, for example) is significantly lower.
Permanent magnetic fields and low frequency alternating fields (50/60 Hz) with low harmonics
content are permissible up to a field strength of 1,000A/m (30mm barrel diameter—80 A/m).
LIQUIDS Due to their one-piece stainless-steel construction, the 871TM Extended Range family of inductive
proximity sensors is naturally suitable for applications where liquids are present. Cable units are
virtually impermeable from a construction standpoint; however, the PUR c able used can have
limitations when faced with various chemicals. The same is true for micro QD models in most cases,
however, some manufacturers’ cor dsets may have a missing or unsuitably dimensioned O-ring on
the connector side c ausing an unstable seal. For this reason, cable models are strongly
recommended in applications where sealing is crucial. To determine the best cabling option for your
application, consult your local Rockwell Automation repr esentative.
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Publication 871TM--UM001A--EN--P – February 2004
Copyright © 2004 Rockwell Automation, Inc.. All rights reserved. Printed in USA.